Modern System-on-Chip (SoC) devices for mobile phone applications support various radio-standards like GSM, Bluetooth, FM radio.
Crosstalk can appear when two standards are operated in parallel. The harmonics of the transmit signal of standard A can fall into the receive band of standard B and can reduce the sensitivity of receive path B.
For example, the 9th harmonic of a 104 MHz FM radio transmit signal couples via the FMR-antenna to the GSM-antenna and falls into the receive band of the GSM 900 standard and reduces the sensitivity of a GSM receive signal located at 936 MHz.